Gear cutting machines for bevel gears, wherein the conventional generating cradle or generating drum has been replaced by a type of a compound carriage, are usually embodied in accordance with the following concept: a tool or cutter head spindle and its drive are located on a first carriage, which performs the vertical portion of the former generating drum rotation. For its part, this carriage is guided on a machine housing, which is displaced on a horizontal guide of the machine base in order for the cutter head to dip into the workpiece. The horizontal part of the former generating drum is in this case performed by a workpiece spindle support. Examples of such machines are recited in what follows.
A problem in the design of such gear cutting machines is the fact that chips generated in the course of gear cutting remain on the horizontal guide tracks on the machine base or on their cover. During wet milling they must be conveyed away by a strong oil flow. With a weak oil flow or with gear cutting without oil, so-called dry milling which is desired for ecological reasons today, considerable problems arise on account of the chips. Since during dry milling the chips absorb 80% of the heat, heat distortion of the guides and of the machine housing and therefore inaccuracies and impediments in the feed movement can arise. Chip removal is expensive, both in connection with wet and dry milling, if machine damage is to be prevented. The ergonomic arrangement of the operating elements is also important when designing such gear cutting machines in order to assure the rapid and safe set-up of the machine tools. This means that for an operator in particular the tool and the workpiece must be easily accessible for changing without having to bend over into the machine.
A machine of the type described in the field of the invention, which is constructed in accordance with the above concept, is represented in USSR Letters Patent 724 287. The tool spindle axis of this machine is arranged at right angles to the straight coordinate axis of the machine housing, in which the machine housing is horizontally guided on the machine base. Furthermore, the tool spindle is located on a side of the machine housing facing away from the operator. A change in tools is therefore connected with a corresponding elaboration. Since furthermore in this embodiment the place where the tool and the workpiece are in engagement during gear cutting is located above the machine base, an accumulation of chips on the machine base and on the guides cannot be avoided.
CNC gear cutting machines are described in the international patent publication WO 89/01838 and in East German Letters Patent 255 296 A1, wherein the tool spindle is respectively disposed parallel with the straight coordinate axis of the machine housing and at right angles to a lateral surface of the machine housing, wherein the respective lateral surface also extends at right angles to the straight coordinate axis of the machine housing. The mentioned chip accumulation therefore also occurs on the guides and on the machine base of these known gear cutting machines. It is furthermore necessary for an operator to bend over into the machine for changing the tool and/or the workpiece.
An advantageous chip run-off into an appropriate collection chamber is assured with lathes, such as are known from German Published, Non-Examined Patent Application DE-OS 24 27 148 or from German Letters Patent 3 921 649. But these are machine tools of a different type, which are not constructed in accordance with the compound carriage concept.
As already mentioned above, in gear cutting machines the operating elements should be ergonomically arranged. This requirement is met, for example, by the gear cutting machine known from the above mentioned East German Letters Patent 255 296 A1, wherein with manual feeding the workpiece can be moved to the operator. The gear cutting machine known from USSR Letters Patent 724 287 mentioned further above does not meet this requirement.
The efficient operation of the known gear cutting machines is furthermore made more difficult because of their high degree of susceptibility to dirt, besides the unergonomic arrangement of the operating elements.